1. Field of the Invention
This invention relates to an airbag restraint unit for protecting a passenger of a vehicle or the like in the event of a serious collision, and more particularly to such an airbag restraint unit of the type wherein an airbag is secured to a storage container storing therein a gas generator, in a manner that gas from the gas generator is introduced into the airbag when the gas generator is operated.
2. Description of the Prior Art
A variety of airbag restraint units for automotive vehicles or the like have been hitherto proposed and put into practical use as disclosed, for example, in Japanese Utility Model Provisional Publication No. 2,38360, Japanese Patent Publication No. 56-43890 and Japanese Utility Model Provisional Publication No. 61-185642.
Such an airbag restraint unit will be briefly discussed with reference to a schematic illustration of FIG. 10, in which the airbag restraint unit is designated by the reference numeral 1. The airbag restraint unit 1 is disposed inside an instrument panel 2 of an automotive vehicle and located such that the top thereof is closed to the inner surface of the instrument panel 2. The airbag restraint unit 1 is fixedly mounted on a support arm 4, which is mounted on a cross member 3. The airbag restraint unit 1 includes a lower base 6 which serves as a container for storing a gas generator 5. An airbag 7 is fixedly secured to the lower base 6 so that gas flows into the airbag 7 when the gas generator 5 is operated to eject gas.
An airbag cover 8 is fixedly secured to the upper end section of the lower base 6 in order to cover the airbag 7 when in a folded state. In the event of a vehicle collision or the like, the airbag 7 is inflated upon being supplied with gas flown from the gas generator 5. The inflated airbag opens the airbag cover 8 and extends or protrudes toward a vehicle passenger to protect the passenger.
Difficulties have been encountered in such a conventional airbag restraint unit, in which it is unavoidable that a clearance or aperture is formed between the airbag 7 and the lower base at an installation section for the airbag. More specifically, in the conventional airbag restraint unit 1, retaining the airbag 7 to the lower base 6 is done by putting the opening side end section of the airbag 7 between the upper open end section (opened to the upper side) of the lower base 6 and a retainer (not shown) of the rectangular frame type, fastened to the upper open end section of the lower base 6 with small screws (not shown). The opening side end section of the airbag 7 is formed with a plurality of cutouts located at the four corner sections of the frame type retainer and at the small screws, and therefore the clearance or aperture is unavoidably formed in an installation section of the airbag 7 to the lower base 6.
Under formation such a clearance or aperture, it is unavoidable that gas ejected from the gas generator 5 leaks out of the airbag restraint unit 1 through the installation section of the airbag 7 to the lower base 6. As a result, it becomes difficult to obtain a sufficient amount of gas to inflate the airbag 7, thereby making impossible an effective use of gas generated from the gas generator 5. Thus, inflation of the airbag 7 is made ineffective so that there is the possibility of the airbag restraining performance for the passenger being deteriorated.
Further difficulties have been encountered in the above conventional airbag restraint unit 1 as set forth below. The gas generator 5 is usually assembled in the airbag restraint unit 1 after other parts are assembled in or at the last step in an assembly process from the view point of safety. During the assembly of the gas generator 5 in the airbag restraint unit 1, the gas generator 5 is first inserted into the lower base 6 through an inserting opening formed at a side end of the lower base 6, and then fixed in position. Fixing of the gas generator 5 inside the lower base 6 is accomplished by allowing a bolt section at the tip end of the gas generator 5 to project out of the lower base 6 through an opening formed at the other side end of the lower base 6, the projected bolt section being fastened to the lower base 6 with a washer and a nut.
However, during such assembly of the gas generator 5 in the airbag restraint unit 1, the distance of insertion of the gas generator 5 in the lower base 6 is considerably long as being generally equal to the length of the cylindrical section of the gas generator 5. Additionally, the opening through which the bolt section of the gas generator 5 is inserted is considerably small. As a result, the advancing direction of the gas generator 5 cannot be determined in the course of insertion of the gas generator during the assembly of the gas generator 5 in the airbag restraint unit 1, and therefore the insertion of the bolt section at the tip end of the gas generator 5 cannot be easily made, thus making difficult the assembly operation of the gas generator 5 in the airbag restraint unit 1. In this connection, the opening for the gas generator bolt section is formed enlarged, in which the washer for the bolt section compensates the defect of the enlarged opening. Additionally, the washer functions to prevent the gas generator 5 from rotating and to locate the gas generator 5. In this regard, the washer is required to be formed into a special complicated shape and produced separate from the container of the gas generator, thereby raising the production cost of the airbag restraint unit 1. Such problems have been required to be solved.